Camshaft adjusters are used in internal combustion engines for varying the control times of combustion chamber valves, in order to variably shape the phase relation between the crankshaft and the camshaft in a defined angular range between a maximum advanced position and a maximum retarded position. The adaptation of the control times to the current load and rotational speed reduces fuel consumption and the emissions. For this purpose, camshaft adjusters are integrated in a drive train by which a torque is transmitted from the crankshaft to the camshaft. This drive train can be constructed, for example, as a belt, chain, or gearwheel drive.
In a hydraulic camshaft adjuster, the driven element and the drive element form one or more pairs of compression chambers that act opposite to each other and can be charged with hydraulic medium. The drive element and the driven element are arranged coaxially. The filling and emptying of individual compression chambers generates a relative movement between the drive element and the driven element. A spring with rotational effect between the drive element and the driven element forces the drive element in a preferred direction relative to the driven element. This preferred direction can be in the same direction or opposite the direction of rotation.
One construction of the hydraulic camshaft adjuster is the vane cell adjuster. The vane cell adjuster has a stator, a rotor, and a drive wheel with external teeth. The rotor is constructed as a driven element that can be locked in rotation usually with the camshaft. The drive element includes the stator and the drive wheel. The stator and the drive wheel are locked in rotation with each other or are alternatively constructed as one piece. The rotor is arranged coaxial to the stator and within the stator. With their radially extending vanes, the rotor and the stator form oppositely acting oil chambers that can be charged by oil pressure and allow a relative rotation between the stator and the rotor. The vanes are constructed either integrally with the rotor or the stator or arranged as “connected vanes” in grooves of the rotor or of the stator provided for these vanes. The vane cell adjusters also have various sealing covers. The stator and the sealing covers are secured with each other by several screw connections.
A different construction of the hydraulic camshaft adjuster is the axial piston adjuster. Here, a displacement element is displaced using oil pressure in the axial direction, which generates, via helical gearing, a relative rotation between a drive element and a driven element.
Another construction of a camshaft adjuster is the electromechanical camshaft adjuster that has a triple-shaft gear (for example, a planetary gear). Here, one of the shafts forms the drive element and a second shaft forms the driven element. By using the third shaft, rotational energy can be fed to the system by a control device, for example, an electric motor or a brake, or energy can be discharged from the system. There can also be a spring that boosts or lessens the relative rotation between the drive element and the driven element.